Abstract: In August 2020, extremely heavy rainfall occurred in the Minjiang River Basin, and the maximum inflow(6 990 m3/s) of Pubugou Reservoir occurred since the reservoir construction, and the flow below Pubugou Reservoir also reached the historical extreme value. In order to study the development characteristics of the rainstorm and flood and the effect of Daduhe River cascade reservoir group in the flood control process, we studied the flood development process, flood composition and magnitude, flood reduction analysis and so on, analyzed the characteristics of the heavy rain and flood, and quantified the effect of joint operation of Daduhe Reservoir group with the Pubugou Reservoir as a core on relieving flood control pressure in the middle and lower reaches of the Daduhe River and Minjiang River. The results showed that:(1) The rainfall on the Dadu River in August 2020 was mainly distributed in the lower reaches of Luding, and had the characteristics of high concentration and strong intensity.(2) The flood of "20·8" of Daduhe River presented the characteristics of many processes, large flood peak magnitude, the encounter of mainstream and tributaries, fierce rising trend of flow and outstanding interval flood volume.(3) The cascade reservoir group, with the core of Pubugou Reservoir, played an important role in flood control, and ensured the safety of Chengdu-Kunming railway, Leshan urban area and the lower reaches of Minjiang River, in addition, decreased the magnitude of flood peak from 100-year return period to normal magnitude for Ebian and Tongjiezi sections in the lower reaches of Dadu River.(4) Considering the flood control demands of Sichuan and Chongqing reaches, the Pubugou reservoir impounded the flood accounting for 8.4 % of the total amount impounded by the reservoirs in the upstream of Cuntan station, which effectively alleviated the flood control pressure of Sichuan and Chongqing reaches.